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Value of HP28C vs 28S?
01-30-2015, 01:16 AM
Post: #1
Value of HP28C vs 28S?
Just getting back into building the collection of HP's RPN Graphers. I remember some saying last time I should look into a 28 series as they were HP's first real graphing calc in the series.

I've been watching E Bay and Amazon for a week now, and have observed that the S usually sells for multiples of the C. Is the only difference the RAM? Is there something else that's really different about the S version? Seems they go for about the price of a 48GX most of the time, so I've really got to think about the value there... Smile

Thanks for any pointers to a 28 series newbie!
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01-30-2015, 01:32 AM
Post: #2
RE: Value of HP28C vs 28S?
Broadly speaking: the 28S had a usable amount of RAM, the 28C didn't.
No other significant differences.


Pauli
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01-30-2015, 03:00 AM
Post: #3
RE: Value of HP28C vs 28S?
Something to watch out for when buying a Clamshell through the internet is to make sure the battery door is unbroken. Many are, due to bad design. Ask- and if you can't get a direct answer then I'd suggest you figure it's a bad deal. Someday, someone will 3d print these but that day wasn't yesterday and it's getting late today.
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01-30-2015, 04:48 AM (This post was last modified: 01-30-2015 04:50 AM by Steve Simpkin.)
Post: #4
RE: Value of HP28C vs 28S?
From this site (http://www.hpmuseum.org/hp28c.htm):

The HP-28C was introduced with 2K bytes of storage. The HP-28S replaced it a year later with 32K bytes at the same price.

The HP-28S also added:

Directories. Directories allowed variables and programs to be grouped together and to allow sets of variables with the same names to be defined in separate directories. To create a directory, the user entered directory name on the stack and entered the CRDIR command. The new directory would appear in the USER menu just like any other object. Directories could be nested. The top directory was HOME and the PATH command displayed the current directory path. CLUSER purged a directory including non-empty subdirectories.

Custom Menu. The user could define a menu of objects/commands with the MENU command and then view this menu with the CUSTOM command. Unlike the USER menu which showed the objects in the current directory, the CUSTOM menu was set by a command and stayed the same even as the user moved through the directory structure.

Graphics Strings. The LCD> command created a string that contained the bits of the current LCD display which could be stored, altered, and printed. >LCD moved a string into the LCD.
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01-30-2015, 05:01 AM
Post: #5
RE: Value of HP28C vs 28S?
(01-30-2015 01:32 AM)Paul Dale Wrote:  Broadly speaking: the 28S had a usable amount of RAM, the 28C didn't.
No other significant differences.

It's hard to overstate how unusable the 28C is/was due to the extremely limited RAM. You had to turn off the UNDO system to get anything useful done. Trying to use any of the CAS functions was nearly impossible, and storing and sort of substantial program/data, forget about it.

The 28S is/was quite useful and fun. Had I paid for my 28C when I got it new, I would have felt really cheated -- but it was a gift from HP for giving a talk at one of their seminar series.

-katie

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01-30-2015, 06:01 AM
Post: #6
RE: Value of HP28C vs 28S?
Thank you all very much, exactly the kind of real user answers I was looking for. Smile I will definitely hold out for the 28S version then, and just kind of put it on the back burner and see if one pops up in my price range for the collection.
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01-30-2015, 07:34 AM
Post: #7
RE: Value of HP28C vs 28S?
(01-30-2015 03:00 AM)Den Belillo (Martinez Ca.) Wrote:  Someday, someone will 3d print these but that day wasn't yesterday and it's getting late today.
The case can break, too, which would be fatal as I heard. Don't know myself, as I have two intact clamshells and a spare door somewhere. But usually the compartement doesn't break if you're careful. Changed batteries many times in my 18C and 19B.

Very nice looking calculators, if only they would open to the other side like the Casios.
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01-30-2015, 04:55 PM
Post: #8
RE: Value of HP28C vs 28S?
I don't use mine at all any more because I'm scared of breaking the covers. :-(

It would be nice if there was a reasonably straight forward way of joining the batteries (electrically) without needing so much spring pressure.
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01-31-2015, 05:32 AM
Post: #9
RE: Value of HP28C vs 28S?
(01-30-2015 01:32 AM)Paul Dale Wrote:  Broadly speaking: the 28S had a usable amount of RAM, the 28C didn't.
No other significant differences.


Pauli

Brian Walsh's 28S review article from the HPX Exchange, Volume 1 Number 4 (1988) is located here, with a list of 33 differences between 28C and 28S. Some are more significant than others, of course.

Jake
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01-31-2015, 08:10 PM (This post was last modified: 01-31-2015 08:11 PM by Dave Dirckx.)
Post: #10
RE: Value of HP28C vs 28S?
I have very nice memories of my HP-28C. I remember solving a linear system of 10 unknowns as the only one (with exact results) during an exam where we were allowed to use any calculator.

I never had the impression that I was fooled by HP when the 28-S came out. I was used to be careful with the memory storage, and for me and some students, it was a calculator with capabilities that were unseen in any other calculator. It was the first RPL, it should be worth something.
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02-05-2015, 08:51 PM
Post: #11
RE: Value of HP28C vs 28S?
(01-30-2015 01:16 AM)Jedidiah Smith Wrote:  Just getting back into building the collection of HP's RPN Graphers. I remember some saying last time I should look into a 28 series as they were HP's first real graphing calc in the series.

I've been watching E Bay and Amazon for a week now, and have observed that the S usually sells for multiples of the C. Is the only difference the RAM? Is there something else that's really different about the S version? Seems they go for about the price of a 48GX most of the time, so I've really got to think about the value there... Smile

Thanks for any pointers to a 28 series newbie!

If you want to buy a 28, go for the 28s, unless you want to have the 28c for collecting purposes.

It is really fun and I think the clamshell design very classy.

As above already stated, the battery door is problematic (by design), so it is very hard to find one integer.

Other thing, be carefull with the batteries. Only put type N batteries, 1, 5 v. I fried a 28s by putting 3 12v batteries, They are almost the same size and fits perfecly.

But I have alraedy bought a mint one, made in Brazil and also bought many N size batteries and I will not mix them with the 12v (normally used for garage door remote control).

Other tip, the Museum Stick driver have some good and usefull books for the 28c/28s,

Good luck, you will love the 28!
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02-10-2015, 01:47 PM
Post: #12
RE: Value of HP28C vs 28S?
(01-30-2015 01:16 AM)Jedidiah Smith Wrote:  I remember some saying last time I should look into a 28 series as they were HP's first real graphing calc in the series.

That's actually debatable - they're certainly the first capable of doing graphing on the calc's display, but the 9100A supported graphing with a plotter, and the 41C could do it with a printer or a HP-IL plotter.
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02-14-2015, 08:16 AM
Post: #13
RE: Value of HP28C vs 28S?
(01-30-2015 05:01 AM)Katie Wasserman Wrote:  It's hard to overstate how unusable the 28C is/was due to the extremely limited RAM.

Good thing I didn't know that at the time. ;-)

The 28C was an invaluable tool during my grad school days in physics. I used it to calculate uncertainties on the fly and to do real time adjustments to measurements to take into account the decreasing strength of a radioactive source.

When I started teaching, I was the only person in the school with a graphing calculator.

I wouldn't want to use it today, but I sure did like using it at the time.
-wes
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02-17-2015, 04:55 PM
Post: #14
RE: Value of HP28C vs 28S?
(02-14-2015 08:16 AM)Wes Loewer Wrote:  
(01-30-2015 05:01 AM)Katie Wasserman Wrote:  It's hard to overstate how unusable the 28C is/was due to the extremely limited RAM.

Good thing I didn't know that at the time. ;-)
.......
I wouldn't want to use it today, but I sure did like using it at the time.

I too loved it when I first got it, it's was an amazing leap forward from anything else available at the time both in graphics and programming. I used it a lot until the 28S came out and I realized how crippled it was becasue of it's RAM size. I was able to use it becasue I learned to avoid anything that required much RAM, so some of the built-in functions I just wouldn't touch (virtually all of the symbolic algebra stuff) and I didn't store any programs on it, because I would likely need that memory for another calculation/program.

-katie

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